Dye stripping solution



- DYE S TRIPPINGSOLUTION NathanielA. Matlin, L evittown, Pa., assignor to Rohm & Haas Company, Philadelphia, Pa., a corporation of Delaware No Drawing. Application December 13, 1955 Serial No. 552,693 r a 6 Claims. cum-10s This invention relates to th e stripping of dyes from textile goods by the use ofreducing agents. It is particularly concerned with an improvement in stripping baths and in processes of stripping in accordance with Which novel scavengers are employed in the stripping bath United States Patent which may have a residual color but of a different hue or tint than that of the original dye. In either event, it is difficult to prevent re-deposition of the leuco form of vat dye or of the somewhat colored residual components of dyes that are decomposed by the reducing agent. In many cases, the stripping operation which utilizes merely a reducing agent serves only to reduce the depth of color or to change the hue to a rather dark yellow. Quaternary ammonium compounds have been used heretofore for the purpose of adsorbing some of the dye or other colored matter that is dissolved in the stripping bath to prevent quaternary ammonium compound containing at least one hydrophobic substituent having at least 8 carbon atoms. These two components of applicants novel scavenger system are employed in quite lowproportions in the stripping baths, and they arebelieved to form a complex colloid salt type of coacervate. Such a coacervate consists of clusters or micelles formed by the interaction of two oppositely charged materials, at least one of which 7 is of relatively high molecular weight.

The scavenger system of the present invention is useful in any aqueous stripping bath containing a reducing agent. The pH of the bath may be from. about 3 to about 13. Examples of reducing agents that may be used include sodium or zinc hyd-rosulfite at pHs greater than 9; sodium or zinc formaldehyde sulfoxylates at low pHs around 3 to 4; basic zinc formaldehyde sulfoxylate, generallyin a pH range of 3 to 7; and thiourea dioxide (formamidine-sulfinic acid) which may be used in any pH within the range of 3 to 13. :The amount of reducing agent may be from 2% to 5% on the Weight of the goods to be stripped of dye. In practice,the concentration of the reducing agent in the aqueous stripping bath may be from 0.01 to 1% on the total weight of the bath and is preferably in the range of 0.02 to 0.25%.

The amount ofithe scavenger system (thatis the'total .of the quaternary ammonium compound and the polymeric acid) may be from about 0.5 to 4% on the weight of the fabric and is preferably about 2% on the weight of the fabric. The concentration of the scavenger system used in the stripping bath may range from 0.01 to 0.10%, that is preferably about 0.05% based on the total weight of the bath liquor. The bath to fabric ratio may be from 20:1 to :1 and is preferably on the order of about 40:1.

The quaternary ammonium compound of the scavenger system may comprise one or more compounds of formula I:

where at least one of R, R", R and R" is an aliphatic, arylaliphatic, or alicyclicaliphatic group having at least 8 carbon atoms, such as octyl, dodecyl, hexadecyl, octadecyl, butylbenzyl, methyl-hexahydrobenzyl, and so on, and any other of R, R R' and R" may be selected individually from such groups as lower alkyl having 1 to 7 carbons, including methyl, ethyl, propyl, isopropyl, butyl, amyl, hexyl, also allyl, methallyl, benzyl, methylbenzyl, 3 hydroxyethyl, 'y hydroxypropyl, ,6 hydroxypropyl, phenoxyethyl, ethoxyethyl, phenoxyethoxyet'hyl, tetrahydrobenzyl, hexahydrobenzyl, and so on, and A is an anion.

Examples of quaternary ammonium compounds that may be used include cetyldimethylethylammonium ethosulfate; cetyldimethylbenzylammonium chloride; laurylpyridim'um chloride; trimethyloctadecylammoni um bromide; (p-t-octylphenoxyethoxyethyl)dimethylbenzylammonium chloride; (p-tolyl-dodecyl)trimethylammonium methosulfate; oleylbenzyldimethylammonium chloride; octadecylpyridinium bromide; cetylpyridinium bromide; octadecyltrimethylammonium iodide; cetyltrimethylammonium bromide; cetyltriethylammonium bromide; ,6- hydroxyethyl-N-octadecyl morpholinium bromide; dodecenyltrimethylammonium ta-rtrate (of Serial No. 531,277, filed August 29, 1955); didodecenyldimethylamrnonium chloride (of 2,706,195). Besides the anions mentioned, any of these compounds may be added as the hydroxides or as salts having other anions, such as bromide, chloride, sulfate, acetate, lactate, tartrate, citrate, phosphate, and glycinate. All of these anions are of non-oxidizing character.

The polymeric acid of the scavenger system may be a simple polymer of acrylic acid, methacrylic acid, itaconic acid, aconitic acid, citraconic acid, maleic acid, fumaric aid, the dimer of methacrylic acid, or the trimer of methacrylic .acid. The polymeric acid may also be a copolymer containing at least 10% by Weight of at least one of the monomeric acids just mentioned. It is essential that the polymeric acid be soluble in water to the extent of at least 0.1%. By water-soluble it is meant to include polymers which produce colloidal dispersions as well as truesolutions. The molecular weight of the polymeric acid should be at least 1500 and is preferably at least 7500. However, the molecular weight may be much higher, such as from 10,000 to 200,000 or more.

The copolymers of the acids mentioned hereinbefore may contain as comonomers oneor more compounds selected from the group consisting of alkyl acrylates, alkyl methacrylates, styrene, acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, vinyl acetate, and the like. Preferred comonomers are the alkyl acrylates or methacrylates in which the alkyl group has from 1 to 4 carbonatoms, such as methyl, ethyl, propyl, and butyl acrylates and methacrylates. 1 e

Stripping'baths of the present invention which contain a reducing agent and the novel scavenger system described hereinaboveareuseful for removing many ty'pesof dyes from a wide variety of textiles. .Thus, these baths serve to remove anthraquinone dyes, azo dyes, and indigoid dyes, being especially useful for vat dyes which are generally the most difiicult to remove. They may be used for stripping these dyes from textile goods of natural'or artificial fibers including cotton, wool, silk, linen, viscose rayon, cuprammonium cellulose rayon; cellulose esters including cellulose acetate, cellulose acetate butyrate; viny l resins such as polymers of vinyl chloride and acrylonitrile, especially those containing 75% to 95% of vinyl chloride or acrylonitrile, copolymerized with other monomers such as vinyl acetate, vinylpyridine, methacrylonitrile or mixtures thereof; polyethylene; polymers of vinylidene chloride including copolymers thereof with vinyl chloride and acrylonitrile; polyamides, especially nylon 66 and caprolactam types; polyesters including especially polyethylene terephthalate; casein, a-protein, and so on.

In carrying out the stripping operation, the stripping bath may be made by dissolving the reducing agent to be used in proper concentration in water. Then the polymeric acid and the quaternary ammonium compound are added separately in either order. If desired, the reducing agent may be added to the stripping bath after the introduction of one or both of the polymeric acid and quaternary ammonium compound. The amounts of polymeric acid and quaternary ammonium compound are generally used in stoichiometrically equivalent proportions. However, an excess of the quaternary ammonium compound may be provided for the purpose of modifying the hand of the stripped goods, that is, for imparting a softer feel thereto. The stripping bath is employed at any temperature from room temperature to the boil at atmospheric pressure or, if desired, up to about 120 C. with a suitable pressure vessel. must, of course, be selected in dependence upon the nature of the goods. Preferably, a temperature of 80 C. to 100 C. is employed for most purposes. For cellulose acetate, it is generally desirable to stay close to 80 C.; 80 to 95 C. is quite useful for W001; about 95 C. is entirely satisfactory for cotton and regenerated cellulose rayon; and temperatures from 95 to 120 C. may be employed with nylon, polymers containing at least 75 acrylonitrile, such as Orlon land Acrilan, and polyethylene terephthalate (Dacron). The goods may be kept within the bath until such time as the stripping operation is completed, during which time it is desirable to provide suitable agitation of the liquor and fabric or other goods. If desired, the fabric may be run repeatedly through the bath until the stripping has been completed.

If desired, the goods after removal from the stripping bath may be subjected to a final supplemental oxidative treatment to remove any residual yellowish color in the textile goods. This may involve treatment with a hypochlorite or a peroxide or perborate, such as those of sodium or potassium.

The employment of the novel scavenger system of the present invention provides a much cleaner or white ground. It appears that the coacervate serves to adsorb the color that is removed from the fabric or other goods and thereby prevents the color from re-depositing. It appears that this action occurs not only when a leuco form of a vat dye is formed but also in the case of non-vats when colored decomposition products are produced from the dye by the reducing agent.

In the following examples, which are illustrative of the present invention, the parts are by weight unless otherwise designated:

Example 1 Cotton, vat dyed blue with 4% 'Indanthrene Blue GOD (an anthraquinone typeColor Index No. 1112), was stripped under conditions of 50:1 bath, 85 (3., pH 12-13, 30 minutes, with:

5% o.w.g. (0.10% w./v.) sodium hydrosulfite o.w.g. (.20% w./v.) NaOH The temperature employed 4- 2% o.w.g. (04% w./v.) polyacrylic acid (PAA), M.W.

10,00020,000 3% o.w.g. (.06% w./v.) (methyldodecylbenzyl)trimethylammonium chloride 'NoTE.Percent in first column based on weight of goods; percent in second column=g./ 100 cc. of bath.

The stripping Was also run with the quaternary alone as additive, and with polyvinylpyrrolidone (PVP) as sole additive to the reducing bath. Results are:

I Color of Goods Additive After Stripping PVP light blue. quaternary dirty blue-gray. quaternary/FAA very faint yellow.

Example 2 As above, two other strippings were run, one with PVP as additive, the other with the quaternary as sole additive:

Additive Color of Stripped Goods PVP light gray. quaternary somewhat darker gray. quaternary/FAA very faint yellow.

Example 3 Cellulose acetate, disperse-dyed a royal blue with 3% Setacyl Blue RF (a modified Primuline type-Color Index prototype No. 228), was stripped at C., 40:1 bath, 30 minutes, with:

5% o.w.g. (0.125% w./v.) zinc formaldehyde sulfoxylate 1% o.w.g. (025% w./v.) polyacrylic acid (PAA) M.W.

1% o.w.g. (.025 w./v.) didodecenyldimethylammonium chloride (U.S. Patent 2,706,195

with enough formic acid added to give a pH of 34. A stripping was also run with the quaternary as sole additive to the reducing bath.

Additive Color of Stripped Goods quaternary pale greenish blue. quaternary/PAL. pale yellow.

Example 4 W001, acid-dyed bright reddish blue with 3% Xylene Milling Blue BL (an azo type color, Color Index No. 833), was scoured in a solution of ammonia and di-isobutylphenoxypolyethoxyethanol and after rinsing was entered wet into the stripping bath:

5% o.w.g. (0.125% w./v.) sodium formaldehyde sulfoxylate 40% by weight of ethyl acrylate and 60% by weight of acrylic acid, molecular weight about 100,000)

1% o.w.g. (025% w./v.) (di-iso-butylcresoxyethyl)dimethylbenzylammonium chloride The stripping was run at 100 C., with enough formic acid to give a pH of 3-4, at 40:1 ratio for 30 minutes. A similar stripping was run with the quaternary as sole additive in the reducing bath.

Additive Color of Stripped Goods quaternary dull, dirty blue. quaternary/acrylic acid copolymer lighter blue.

Example 5 Cotton, direct-dyed blue with 5% Pontamine Sky Blue FF, was stripped at 50:1, 100 C., 30 minutes, in:

5% o.w.g. (0.10% w./v.) sodium hydrosulfite 1.5% o.w.g. (03% w./v.) 40/60 EA/AA, M.W. ca.

2% o.w.g. (.04% w./v.) (methy-ldodecenylbenzyl)trimethylammonium chloride with enough soda ash (N a CO to give a pH of ca. -11. Strippings were also run with PVP and with the quaternary as sole additives to the reducing bath:

Additive Color of Stripped Goods PVP quaternary quaternary/acrylic acid copolymer light blue. somewhat darker blue. dull white.

Example 6 Cotton, vat-dyed blue with 8% Indigo (Color Index No. 1177), was stripped at 100:1, 90 C., 30 mins., pH 12-13, in:

Strippings were also run with PVP as sole additive, and with the quaternary as sole additive to the reducing bath:

Additive Color of Stripped Goods IPVP quaternary quaternary/methacrylic acid copolymer light blue.

Do. faintly yellowish white.

It is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. An aqueous composition'comprising a solution in water of 0.01 to 1% of a reducing agent selected from the group consisting of hydrosulfites, aldehyde, sulfoxylates and sulfinic acids, a quaternary ammonium compound containing a hydrophobic substituent having at least 8 carbon atoms and having the Formula I:

where at least one of R, R, R, and R" is selected from the group consisting of aliphatic, aryl-aliphatic, and alicyclicaliphatic groups having at least 8 carbon atoms, and each of any other of the R, R", R, and R" radicals is selected individually from the group consisting of lower alkyl groups having 1 to 7 carbon atoms, allyl, methallyl,

benzyl, methylbenzyl, fl-hydroxyethyl, 'y-hydroxypropyl, phenoxyethyl, ethoxyethyl, phenoxyethoxyethyl, tetrahydrobenzyl, and hexahydrobenzyl, and A is an anion of non-oxidizing character, and a water-soluble polymeric acid having a molecular Weight of at least 1,500 to 200,000, the concentration of the polymeric acid being about 0.01 to 0.04% and the concentration of the quaternary ammonium compound being about 0.-01 to 0.06%.

2. An aqueous composition comprising a solution in Water of 0.01 to 1% of a reducing agent selected from the group consisting of hydrosulfites, aldehyde sulfoxylates, and sulfinic acids, a quaternary ammonium compound containing a hydrophobic substituent having at least 8 carbon atoms and having the Formula I as defined in claim 1, and a water-soluble polymeric acid having a molecular weight of at least 1,500 to 200,000 selected from the group consisting of polymers of an acid selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, aconitic caid, citraconic acid, maleic acid, and fumaric aid, the concentration of the quaternary ammonium compound being about 0.01 to 0.06% and the concentration of the polymeric acid being about 0.01 to 0.04%.

3. A composition as defined in claim 2 in which the polymer is a copolymer containing at least 10% by weight of at least one of the acids mentioned.

4. An aqueous composition comprising a solution in water of 0.01 to 1% of a reducing agent selected from the group consisting of hydrosulfites, aldehyde sulfoxylates, and sulfinic acids, a quaternary ammonium compound containing a hydrophobic substituent having at least 8 carbon atoms and having the Formula I as defined in claim 1, and a Water-soluble polymer of acrylic acid having a molecular weight of at least 1,500 to 200,000, the concentration of the quaternary ammonium compound being about 0.01 to 0.06% and the concentration of the polymeric acid being about 0.01 to 0.04%.

5. An aqueous composition comprising a solution in water of 0.01 to 1% of a reducing agent selected from the group consisting of hydrosulfites, aldehyde sulfoxylates, and sulfinic acids, a quaternary ammonium compound containing a hydrophobic substituent having at least 8 carbon atoms and having the Formula I as defined in claim 1, and polyacrylic acid having a molecular weight of at least 1,500 to 200,000, the concentration of the quaternary ammonium compound being about 0.01 to 0.06% and the concentration of the polymeric acid being about 0.01 to 0.04%.

6. An aqueous composition comprising a solution in water of 0.01 to 1% of a reducing agent selected from the group consisting of hydrosulfites, aldehyde sulfoxylates, and sulfinic acids, 0.01 to 0.06% of a quaternary ammonium compound containing a hydrophobic substituent having at least 8 carbon atoms and having the structure of Formula I as defined in claim 1 and 0.01 to 0.04% of a copolymer of methacrylic acid with an ester of an alcohol having 1 to 4 carbon atoms with an acid of the formula where n is an integer having a value of 1 to 2, having a molecular weight of at least 1,500 to 200,000.

References Cited in the file of this patent UNITED STATES PATENTS 2,548,892 Gooding et a1 Apr. 17, 1951 2,548,914 Seiter et al. Apr. 17, 1951 2,549,079 Gooding et al. Apr. 17, 1951 OTHER REFERENCES Du Pont, Tech. BulL, vol. 7, No. 1, page 11, March 1951. 

1. AN AQUEOUS COMPOSITION COMPRISING A SOLUTION IN WATER OF 0.01 TO 1% OF A REDUCING AGENT SELECTED FROM THE GROUP CONSISTING OF HYDROSULFITES, ALDEHYDE, SULFOXYLATES AND SULFINIC ACIDS, A QUATERNARY AMMONIUM COMPOUND CONTAINING A HYDROPHOBIC SUBSTITUENT HAVING AT LEAST 8 CARBON ATOMS AND HAVING THE FORMULA 1: 